Hem portions of various clothing are finished by hem sewing in which an edge part of cloth is turned back across a predetermined width and then folded under the remaining portion and, after that, the vicinity of the edge is sewed up. When the hem sewing is to be performed by using a common sewing machine, the work of turning back and folding, while maintaining a constant width, the edge of the cloth fed to a needle location position is to be performed by hand. This work needs skill and there is a possibility of causing various poor sewing like the folding width is insufficient so that some portions are not allowed to be sewed up and, on the contrary, the folding width is excessive so that a seam line is formed at a position distant from the edge.
In view of such situations, a sewing machine for hem has been proposed that comprises a turn-back device provided in front of the needle location position and is thereby capable of implementing satisfactory hem sewing without the necessity of skill (for example, see Japanese Patent Application Laid-Open No. H10-235054). The turn-back device includes: a guide plate that is located in a recess provided in front of the needle location position and that protrudes in parallel to a needle plate; a ruler member extending in parallel to an upper face of the guide plate and then being bent at a position opposing a tip part of the guide plate so as to be continuous to the bottom face of the recess; and an air ejection outlet being opened in the bent part of the ruler member and ejecting air to a space between the guide plate and the recess. Cloth is supplied along the upper face of the guide plate in a state that an edge part thereof is bent along the bent part of the ruler member. Then, the cloth is fed out in a direction along the tip part of the guide plate. The air ejected from the air ejection outlet flows through a space between a lower face of the guide plate and the recess at a high speed and thereby biases the cloth overlapping with the lower face of the guide plate toward a direction substantially perpendicular to the feed direction so as to press the edge of the cloth against an end face of the recess.
In the sewing machine for hem, the cloth introduced into the turn-back device is folded one above the other with the guide plate in between. Then, by virtue of the above-described pressing to the end face of the recess, the folding width of the edge part has a substantially fixed value corresponding to the amount of protrusion of the guide plate. Thus, it is sufficient that an operator performs the work of holding the cloth in front of the turn-back device so as to assist the introduction into the turn-back device. Accordingly, hem sewing is allowed to be simply implemented.